Morphology of the Nuclear Disk in M87

A deep, fuly sampled diffraction limited (FWHM ~ 70 mas) narrow-band image of the central region in M87 was obtained with the Wide Filed and Planetary Camera 2 of the Hubble Space Telescope using the dithering technique. The H-alpha+[NII] continuum subtracted image reveals a wealth of details in the gaseous disk structure described earlier by Ford et al. (1994). The disk morphology is dominated by a well defined three-arm spiral pattern. In addition, the major spiral arms contain a large number of small "arclets" covering a range of sizes (0.1-0.3 arcsec = 10-30 pc). The overall surface brightness profile inside a radius ~1.5" (100 pc) is well represented by a power-law I(mu) ~ mu^(-1.75), but when the central ~40 pc are excluded it can be equally well fit by an exponential disk. The major axis position angle remains constant at about PA_disk ~ 6 deg for the innermost ~1", implying the disk is oriented nearly perpendicular to the synchrotron jet (PA_jet ~ 291 deg). At larger radial distances the isophotes twist, reflecting the gas distribution in the filaments connecting to the disk outskirts. The ellipticity within the same radial range is e = 0.2-0.4, which implies an inclination angle of i~35 deg. The sense of rotation combined with the dust obscuration pattern indicate that the spiral arms are trailing.Comment: 5 pages, 3 postscript figures, to appear in the Proceedings of the M87 Workshop, Ringberg castle, Germany, 15-19 Sep 1997, also available from http://jhufos.pha.jhu.edu/~zlatan/papers.htm

Remote Sensing of Chiral Signatures on Mars

We describe circular polarization as a remote sensing diagnostic of chiral signatures which may be applied to Mars. The remarkable phenomenon of homochirality provides a unique biosignature which can be amenable to remote sensing through circular polarization spectroscopy. The natural tendency of microbes to congregate in close knit communities would be beneficial for such a survey. Observations of selected areas of the Mars surface could reveal chiral signatures and hence explore the possibility of extant or preserved biological material. We describe a new instrumental technique that may enable observations of this form.Comment: 14 pages, 3 figures; to be published in Planetary and Space Scienc

Time-lapse 3-D measurements of a glucose biosensor in multicellular spheroids by light sheet fluorescence microscopy in commercial 96-well plates

Light sheet fluorescence microscopy has previously been demonstrated on a commercially available inverted fluorescence microscope frame using the method of oblique plane microscopy (OPM). In this paper, OPM is adapted to allow time-lapse 3-D imaging of 3-D biological cultures in commercially available glass-bottomed 96-well plates using a stage-scanning OPM approach (ssOPM). Time-lapse 3-D imaging of multicellular spheroids expressing a glucose Förster resonance energy transfer (FRET) biosensor is demonstrated in 16 fields of view with image acquisition at 10 minute intervals. As a proof-of-principle, the ssOPM system is also used to acquire a dose response curve with the concentration of glucose in the culture medium being varied across 42 wells of a 96-well plate with the whole acquisition taking 9 min. The 3-D image data enable the FRET ratio to be measured as a function of distance from the surface of the spheroid. Overall, the results demonstrate the capability of the OPM system to measure spatio-temporal changes in FRET ratio in 3-D in multicellular spheroids over time in a multi-well plate format

Temporal behavior of the inverse spin Hall voltage in a magnetic insulator-nonmagnetic metal structure

It is demonstrated that upon pulsed microwave excitation, the temporal behavior of a spin-wave induced inverse spin Hall voltage in a magnetic insulator-nonmagnetic metal structure is distinctly different from the temporal evolution of the directly excited spin-wave mode from which it originates. The difference in temporal behavior is attributed to the excitation of long-lived secondary spin-wave modes localized at the insulator-metal interface

A broad look at charcoal rot in the Northern Region broadacre crops through soil sampling and in-crop surveys

Macrophomina phaseolina (Tassi) Goid. is a generalist soil-born pathogen, which is endemic to Australia. The pathogen has a broad host-range of both monocot and dicot plant species which include numerous weed and crop plant species (1, 2). The disease is most commonly identified with summer crops, e.g. soybean, sorghum, sunflower, maize and mungbean (3) and occurs most often when hot, dry conditions occur during the growing season. Current estimates predict that north-eastern Australia will become hotter and dryer as a result of climate change (4, 5). Thus, it is likely that conditions favouring the development of this disease will become more common in the future. However, to date, no work has been done to determine the extent of the pathogen’s presence in Australian soils, in-paddock spatial variability, or the occurrence of the disease as correlated with pathogen presence and population levels. In this paper, we present findings from soil sampling and end-of-season disease assessments in sorghum paddocks across northern New South Wales (NNSW), south eastern Queensland (SEQ) and central Queensland (CQ) during the 2016/17 and 2017/18 summer cropping seasons

Low spin wave damping in the insulating chiral magnet Cu2_{2}OSeO3_{3}

Chiral magnets with topologically nontrivial spin order such as Skyrmions have generated enormous interest in both fundamental and applied sciences. We report broadband microwave spectroscopy performed on the insulating chiral ferrimagnet Cu$_{2}$OSeO$_{3}$. For the damping of magnetization dynamics we find a remarkably small Gilbert damping parameter of about $1\times10^{-4}$ at 5 K. This value is only a factor of 4 larger than the one reported for the best insulating ferrimagnet yttrium iron garnet. We detect a series of sharp resonances and attribute them to confined spin waves in the mm-sized samples. Considering the small damping, insulating chiral magnets turn out to be promising candidates when exploring non-collinear spin structures for high frequency applications.Comment: 5 pages, 5 figures, and supplementary materia

The long-period Galactic Cepheid RS Puppis - III. A geometric distance from HST polarimetric imaging of its light echoes

As one of the most luminous Cepheids in the Milky Way, the 41.5-day RS Puppis is an analog of the long-period Cepheids used to measure extragalactic distances. An accurate distance to this star would therefore help anchor the zero-point of the bright end of the period-luminosity relation. But, at a distance of about 2 kpc, RS Pup is too far away for measuring a direct trigonometric parallax with a precision of a few percent with existing instrumentation. RS Pup is unique in being surrounded by a reflection nebula, whose brightness varies as pulses of light from the Cepheid propagate outwards. We present new polarimetric imaging of the nebula obtained with HST/ACS. The derived map of the degree of linear polarization pL allows us to reconstruct the three-dimensional structure of the dust distribution. To retrieve the scattering angle from the pL value, we consider two different polarization models, one based on a Milky Way dust mixture and one assuming Rayleigh scattering. Considering the derived dust distribution in the nebula, we adjust a model of the phase lag of the photometric variations over selected nebular features to retrieve the distance of RS Pup. We obtain a distance of 1910 +/- 80 pc (4.2%), corresponding to a parallax of 0.524 +/- 0.022 mas. The agreement between the two polarization models we considered is good, but the final uncertainty is dominated by systematics in the adopted model parameters. The distance we obtain is consistent with existing measurements from the literature, but light echoes provide a distance estimate that is not subject to the same systematic uncertainties as other estimators (e.g. the Baade-Wesselink technique). RS Pup therefore provides an important fiducial for the calibration of systematic uncertainties of the long-period Cepheid distance scale.Comment: 14 pages, 14 figures, accepted for publication in Astronomy & Astrophysic

Long-term effect of temperature on honey yield and honeybee phenology

There is growing concern about declines in pollinator species, and more recently reservations have been expressed about mismatch in plant-pollinator synchrony as a consequence of phenological change caused by rising temperatures. Long-term changes in honeybee Apis mellifera phenology may have major consequences for agriculture, especially the pollinator market, as well as for honey production. To date, these aspects have received only modest attention. In the current study, we examine honeybee and beekeeping activity in southern Poland for the period 1965–2010, supplemented by hive yields from a beekeeper in southern UK in the same period. We show that despite negative reports on honeybee condition, and documented climate change, the studied apiary managed to show a marked increase in honey production over the 46 year study period, as did that from the UK. The proportion of the annual yield originating from the first harvest decreased during the study period and was associated with rising temperatures in summer. Honeybee spring phenology showed strong negative relationships with temperature but no overall change through time because temperatures of key early spring months had not increased significantly. In contrast, increasing yields and an increased number of harvests (and hence a later final harvest and longer season) were detected and were related to rising temperatures in late spring and in summer

Dynamics of magnetization coupled to a thermal bath of elastic modes

We study the dynamics of magnetization coupled to a thermal bath of elastic modes using a system plus reservoir approach with realistic magnetoelastic coupling. After integrating out the elastic modes we obtain a self-contained equation for the dynamics of the magnetization. We find explicit expressions for the memory friction kernel and hence, {\em via} the Fluctuation-Dissipation Theorem, for the spectral density of the magnetization thermal fluctuations. For magnetic samples in which the single domain approximation is valid, we derive an equation for the dynamics of the uniform mode. Finally we apply this equation to study the dynamics of the uniform magnetization mode in insulating ferromagnetic thin films. As experimental consequences we find that the fluctuation correlation time is of the order of the ratio between the film thickness, $h$, and the speed of sound in the magnet and that the line-width of the ferromagnetic resonance peak should scale as $B_1^2h$ where $B_1$ is the magnetoelastic coupling constant.Comment: Revised version as appeared in print. 12 pages 9 figure